Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758100Ab1FWNXQ (ORCPT ); Thu, 23 Jun 2011 09:23:16 -0400 Received: from cantor2.suse.de ([195.135.220.15]:36048 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756160Ab1FWNXP (ORCPT ); Thu, 23 Jun 2011 09:23:15 -0400 Date: Thu, 23 Jun 2011 15:23:12 +0200 From: Michal Hocko To: Hiroyuki Kamezawa Cc: KAMEZAWA Hiroyuki , Christoph Hellwig , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton , Hugh Dickins , Rik van Riel , Michel Lespinasse , Mel Gorman , Lutz Vieweg Subject: Re: [PATCH] mm: preallocate page before lock_page at filemap COW. (WasRe: [PATCH V2] mm: Do not keep page locked during page fault while charging it for memcg Message-ID: <20110623132312.GI31593@tiehlicka.suse.cz> References: <20110622120635.GB14343@tiehlicka.suse.cz> <20110622121516.GA28359@infradead.org> <20110622123204.GC14343@tiehlicka.suse.cz> <20110623150842.d13492cd.kamezawa.hiroyu@jp.fujitsu.com> <20110623074133.GA31593@tiehlicka.suse.cz> <20110623170811.16f4435f.kamezawa.hiroyu@jp.fujitsu.com> <20110623090204.GE31593@tiehlicka.suse.cz> <20110623190157.1bc8cbb9.kamezawa.hiroyu@jp.fujitsu.com> <20110623115855.GF31593@tiehlicka.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1868 Lines: 52 On Thu 23-06-11 22:01:40, Hiroyuki Kamezawa wrote: > 2011/6/23 Michal Hocko : > > On Thu 23-06-11 19:01:57, KAMEZAWA Hiroyuki wrote: > >> On Thu, 23 Jun 2011 11:02:04 +0200 > >> Michal Hocko wrote: > >> > >> > On Thu 23-06-11 17:08:11, KAMEZAWA Hiroyuki wrote: > >> > > On Thu, 23 Jun 2011 09:41:33 +0200 > >> > > Michal Hocko wrote: > >> > [...] > >> > > > Other than that: > >> > > > Reviewed-by: Michal Hocko > >> > > > > >> > > > >> > > I found the page is added to LRU before charging. (In this case, > >> > > memcg's LRU is ignored.) I'll post a new version with a fix. > >> > > >> > Yes, you are right. I have missed that. > >> > This means that we might race with reclaim which could evict the COWed > >> > page wich in turn would uncharge that page even though we haven't > >> > charged it yet. > >> > > >> > Can we postpone page_add_new_anon_rmap to the charging path or it would > >> > just race somewhere else? > >> > > >> > >> I got a different idea. How about this ? > >> I think this will have benefit for non-memcg users under OOM, too. > > > > Could you be more specific? I do not see how preallocation which might > > turn out to be pointless could help under OOM. > > > > We'll have no page allocation under lock_page() held in this path. > I think it is good. But it can also cause that the page, we are about to fault in, is evicted due to allocation so we would have to do a major fault... This is probably not that serious, though. -- Michal Hocko SUSE Labs SUSE LINUX s.r.o. Lihovarska 1060/12 190 00 Praha 9 Czech Republic -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/